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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,207 records · Page 67
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Pushing the limits of high-resolution polymer microscopy using antioxidants

High-resolution transmission electron microscopy (HRTEM) has been transformative to the field of polymer science, enabling the direct imaging of molecular structures. Although some materials have remarkable stability under electron beams, most HRTEM studies are limited by the electron dose the sample can handle. Beam damage of conjugated polymers is not yet fully understood, but it has been suggested that the diffusion of secondary reacting species may play a role. As such, we examine the effect of the addition of antioxidants to a series of solution-processable conjugated polymers as an approach to mitigating beam damage. Characterizing the effects of beam damage by calculating critical dose D c values from the decay of electron diffraction peaks shows that beam damage of conjugated polymers in the TEM can be minimized by using antioxidants at room temperature, even if the antioxidant does not alter or incorporate into polymer crystals. As a consequence, the addition of antioxidants pushes the resolution limit of polymer microscopy, enabling imaging of a 3.6Å lattice spacing in poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3"-di(2-octyldodecyl)-2,2';5',2";5",2"-quaterthiophene-5,5"-diyl)] (PffBT4T-2OD).

36 MATERIALS SCIENCE↗
DOE OSTI2025

Exploring HOD-dependent systematics for the DESI 2024 Full-Shape galaxy clustering analysis

We analyze the robustness of the DESI 2024 cosmological inference from the full shape of the galaxy power spectrum to uncertainties in the Halo Occupation Distribution (HOD) model of the galaxy-halo connection and the choice of priors on nuisance parameters. We assess variations in the recovered cosmological parameters across a range of mocks populated with different HOD models and find that shifts are often greater than 20% of the expected statistical uncertainties from the DESI data. We encapsulate the effect of such shifts in terms of a systematic covariance term, C HOD , and an additional diagonal contribution quantifying the impact of our choice of nuisance parameter priors on the ability of the effective field theory (EFT) model to correctly recover the cosmological parameters of the simulations. These two covariance contributions are designed to be added to the usual covariance term, C stat , describing the statistical uncertainty in the power spectrum measurement, in order to fairly represent these sources of systematic uncertainty. This novel approach should be more general and robust to the choice of model or additional external datasets used in cosmological fits than the alternative approach of adding systematic uncertainties to the recovered marginalised parameter posteriors. We compare the approaches within the context of a fixed ΛCDM model and demonstrate that our method gives conservative estimates of the systematic uncertainty that nevertheless have little impact on the final posteriors obtained from DESI data.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Measurement of the 𝐶⁢𝑃 asymmetry in 𝐷 + → 𝜋 + ⁢𝜋 0 decays at Belle II

We measure the 𝐶⁢𝑃 asymmetry in 𝐷 + → 𝜋 + ⁢𝜋 0 decays reconstructed in 𝑒 + ⁢𝑒 − collisions at the Belle II experiment using a dataset corresponding to an integrated luminosity of 428 fb −1 . A control sample of 𝐷 + → 𝜋 + ⁢𝐾$^0_𝑆$ decays is used to correct for detection and production asymmetries. The result 𝐴 𝐶⁢𝑃 ⁡(𝐷 + → 𝜋 + ⁢𝜋 0 ) = (−1.8 ± 0.9 ± 0.1)%, where the first uncertainty is statistical and the second systematic, is the most precise determination to date. It agrees with the prediction of 𝐶⁢𝑃 symmetry from the standard model and with results of previous measurements.

CP violation↗
DOE OSTI2024

New graph-neural-network flavor tagger for Belle II and measurement of sin 2⁢𝜙 1 in 𝐵 0 → 𝐽/𝜓⁢𝐾$^0_ S$ decays

We present GFlaT, a new algorithm that uses a graph-neural-network to determine the flavor of neutral 𝐵 mesons produced in ϒ⁡(4⁢𝑆) decays. It improves previous algorithms by using the information from all charged final-state particles and the relations between them. We evaluate its performance using 𝐵 decays to flavor-specific hadronic final states reconstructed in a 362 fb −1 sample of electron-positron collisions collected at the ϒ⁡(4⁢𝑆) resonance with the Belle II detector at the SuperKEKB collider. We achieve an effective tagging efficiency of (37.40 ± 0.43 ± 0.36%), where the first uncertainty is statistical and the second systematic, which is 18% better than the previous Belle II algorithm. Demonstrating the algorithm, we use 𝐵 0 →𝐽/𝜓⁢𝐾$^0_ S$ decays to measure the mixing-induced and direct 𝐶⁢𝑃 violation parameters, 𝑆 = (0.724 ± 0.035 ± 0.009) and 𝐶 = (−0.035 ± 0.026 ± 0.029).

CP violation↗
DOE OSTI2025

Search for lepton-flavor-violating ${\tau }^{-}\to {{\ell}}^{-}{K}_{s}^{0}$ decays at Belle and Belle II

We present the results of a search for charged-lepton-flavor violating decays ${\tau }^{-}\to {{\ell}}^{-}{K}_{s}^{0}$, where ℓ − is either an electron or a muon. We combine e + e − data samples recorded by the Belle II experiment at the SuperKEKB collider (428 fb −1 ) with samples recorded by the Belle experiment at the KEKB collider (980 fb −1 ) to obtain a sample of 1.3 billion e + e − → τ + τ − events. We observe 0 and 1 events and set 90% confidence level upper limits of 0.8 × 10 −8 and 1.2 × 10 −8 on the branching fractions of the decay modes ${\tau }^{-}\to {e}^{-}{K}_{S}^{0}$ and ${\tau }^{-}\to {\mu }^{-}{K}_{S}^{0}$, respectively. These are the most stringent upper limits to date.

beyond Standard Model↗
DOE OSTI2024

Study of Υ(10753) decays to π+π−Υ(nS) final states at Belle II

Abstract We present an analysis of the processe + e − →π + π − Υ(nS) (wheren= 1, 2, or 3) reconstructed in 19.6 fb −1 of Belle II data during a special run of the SuperKEKB collider at four energy points near the peak of the Υ(10753) resonance. By analyzing the mass distribution of theπ + π − Υ(nS) system and the Born cross sections of thee + e − →π + π − Υ(nS) process, we report the first observation of Υ(10753) decays to theπ + π − Υ(1S) andπ + π − Υ(2S) final states, and find no evidence for decays toπ + π − Υ(3S). Possible intermediate states in theπ + π − Υ(1S,2S) transitions are also investigated, and no evidence for decays proceeding via the$$ {\pi}^{\mp }{Z}_b^{\pm } $$ π ∓ Z b ± orf 0 (980)Υ(nS) intermediate states is found. We measure Born cross sections for thee + e − →π + π − Υ(nS) process that, combined with results from Belle, obtain the mass and width of Υ(10753) to be (10756.6 ± 2.7 ± 0.9) MeV/c 2 and (29.0 ± 8.8 ± 1.2) MeV, respectively. The relative ratios of the Born cross sections at the Υ(10753) resonance peak are also reported for the first time.

Physics↗
DOE OSTI2025

Reproducibility of fixed-node diffusion Monte Carlo across diverse community codes: The case of water–methane dimer

Fixed-node diffusion quantum Monte Carlo (FN-DMC) is a widely trusted many-body method for solving the Schrödinger equation, known for its reliable predictions of material and molecular properties. Furthermore, its excellent scalability with system complexity and near-perfect utilization of computational power make FN-DMC ideally positioned to leverage new advances in computing to address increasingly complex scientific problems. Even though the method is widely used as a computational gold standard, reproducibility across the numerous FN-DMC code implementations has yet to be demonstrated. This difficulty stems from the diverse array of DMC algorithms and trial wave functions, compounded by the method’s inherent stochastic nature. Here, this study represents a community-wide effort to assess the reproducibility of the method, affirming that yes, FN-DMC is reproducible (when handled with care). Using the water–methane dimer as the canonical test case, we compare results from eleven different FN-DMC codes and show that the approximations to treat the non-locality of pseudopotentials are the primary source of the discrepancies between them. In particular, we demonstrate that, for the same choice of determinantal component in the trial wave function, reliable and reproducible predictions can be achieved by employing the T-move, the determinant locality approximation, or the determinant T-move schemes, while the older locality approximation leads to considerable variability in results. These findings demonstrate that, with appropriate choices of algorithmic details, fixed-node DMC is reproducible across diverse community codes—highlighting the maturity and robustness of the method as a tool for open and reliable computational science.

Della Pia, Flaviano [Univ. of Cambridge (United Ki↗
DOE OSTI2021

Generalizable coordination of large multiscale workflows: challenges and learnings at scale

The advancement of machine learning techniques and the heterogeneous architectures of most current supercomputers are propelling the demand for large multiscale simulations that can automatically and autonomously couple diverse components and map them to relevant resources to solve complex problems at multiple scales. Nevertheless, despite the recent progress in workflow technologies, current capabilities are limited to coupling two scales. In the first-ever demonstration of using three scales of resolution, we present a scalable and generalizable framework that couples pairs of models using machine learning and in situ feedback. We expand upon the massively parallel Multiscale Machine-Learned Modeling Infrastructure (MuMMI), a recent, award-winning workflow, and generalize the framework beyond its original design. We discuss the challenges and learnings in executing a massive multiscale simulation campaign that utilized over 600,000 node hours on Summit and achieved more than 98% GPU occupancy for more than 83% of the time. We present innovations to enable several orders of magnitude scaling, including simultaneously coordinating 24,000 jobs, and managing several TBs of new data per day and over a billion files in total. Finally, we describe the generalizability of our framework and, with an upcoming open-source release, discuss how the presented framework may be used for new applications.

Bhatia, Harsh↗
DOE OSTI2023

Angular analysis of the low K + K – invariant mass enhancement in B + →K + K – π + decays

We study the decay B + →K + K – π + and investigate the angular distribution of K + K – pairs with invariant mass below 1.1 GeV / c 2 . This region exhibits both a strong enhancement in signal and very large direct CP violation. We construct a coherent sum model for the angular distribution of the S- and P-wave, and report the ratio of their amplitudes, the relative phase and the forward-backward asymmetry. We also report absolute differential branching fractions and direct CP asymmetry for the decay in bins of M K+K– and the differential branching fractions in bins of M K+π– . The results are based on a data sample that contains 772 × 10 6 $B\bar{B}$ pairs collected at the $Υ$(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e – collider. The result favors the presence of S- and D-waves in low M K+K– region to the detriment of a P-wave.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Measurement of the branching fraction of Λ + 𝑐 →𝑝⁢𝐾 0 𝑆⁢ 𝜋 0 at Belle

We report a precise measurement of the ratio of branching fractions ℬ⁡(Λ$^+_𝑐$ → 𝑝⁢𝐾$^0_𝑆$⁢𝜋 0 )/ℬ⁡(Λ$^+_𝑐$ → 𝑝⁢𝐾 − ⁢𝜋 + ) using 980 fb −1 of 𝑒 + ⁢𝑒 − data from the Belle experiment. We obtain a value of ℬ⁡(Λ$^+_𝑐$ → 𝑝⁢𝐾$^0_𝑆$⁢𝜋 0 )/ℬ⁡(Λ$^+_𝑐$ → 𝑝⁢𝐾 − ⁢𝜋 + ) =0.339 ±0.002 ±0.009, where the first and second uncertainties are statistical and systematic, respectively. This Belle result is consistent with the previous measurement from the CLEO experiment but has a fivefold improvement in precision. By combining our result with the world average ℬ⁡(Λ$^+_𝑐$ → 𝑝⁢𝐾 − ⁢𝜋 + ), we obtain the absolute branching fraction ℬ⁡(Λ$^+_𝑐$ → 𝑝⁢𝐾$^0_𝑆$⁢𝜋 0 ) =(2.12 ± 0.01 ±0.05 ±0.10)%, where the uncertainties are statistical, systematic, and the uncertainty in the absolute branching fraction scale ℬ⁡(Λ$^+_𝑐$ → 𝑝⁢𝐾 − ⁢𝜋 + ), respectively. This measurement can shed light on hadronic decay mechanisms in charmed baryon decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Measurement of the branching fraction, polarization, and time-dependent C P asymmetry in B 0 → ρ + ρ − decays and constraint on the CKM angle ϕ 2

We present a measurement of the branching fraction and fraction of longitudinal polarization of B 0 → ρ + ρ − decays, which have two π 0 ’s in the final state. We also measure time-dependent C P violation parameters for decays into longitudinally polarized ρ + ρ − pairs. This analysis is based on a data sample containing ( 387 ± 6 ) × 10 6 ϒ ( 4 S ) mesons collected with the Belle II detector at the SuperKEKB asymmetric-energy e + e − collider in 2019–2022. We obtain B ( B 0 → ρ + ρ − ) = ( 2.8 9 − 0.22 + 0.23 − 0.27 + 0.29 ) × 10 − 5 , f L = 0.92 1 − 0.025 + 0.024 − 0.015 + 0.017 , S = − 0.26 ± 0.19 ± 0.08 , and C = − 0.02 ± 0.1 2 − 0.05 + 0.06 , where the first uncertainties are statistical and the second are systematic. We use these results to perform an isospin analysis to constrain the Cabibbo-Kobayashi-Maskawa angle ϕ 2 and obtain two solutions; the result consistent with other Standard Model constraints is ϕ 2 = ( 92.6 − 4.7 + 4.5 ) ° . Published by the American Physical Society 2025

Adachi, I. (ORCID:0000000322870173)↗
DOE OSTI2025

Search for Lepton-Flavor-Violating Decay Modes 𝐵 0 →𝐾$^0_𝑆$⁢𝜏 ± ⁢ℓ ∓ with Hadronic 𝐵 Tagging at Belle and Belle II

We present the first search for the lepton-flavor-violating decay modes 𝐵 0 →𝐾$^0_𝑆$⁢𝜏 ± ⁢ℓ ∓ (ℓ=𝜇,𝑒) using the 711 and 365 fb −1 data samples recorded by the Belle and Belle II detectors, respectively. We use a hadronic 𝐵-tagging technique to fully reconstruct a 𝐵 meson and search for signal decays in the system recoiling against the tagged meson, considering 𝜏 decays to either light leptons, one charged hadron, or one charged hadron and a neutral pion. We find no evidence for 𝐵 0 →𝐾$^0_𝑆$⁢𝜏 ± ⁢ℓ ∓ decays and set 90% confidence level upper limits on the branching fractions in the range of [0.8,3.6] ×10 −5 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Chemical insights into the multi-regime low-temperature oxidation of di-n-propyl ether: Jet-stirred reactor experiments and kinetic modeling

To further understand the combustion characteristics and the reaction pathways of acyclic ethers, in this work the oxidation of di-n-propyl ether (DPE) was investigated in a jet-stirred reactor (JSR) combined with a photoionization molecular-beam mass spectrometer. The experiments were carried out at near-atmospheric pressure (700 Torr) and over a temperature range of 425–850 K. Based on the experimental data and previous studies on ether oxidation, a new kinetic model was constructed and used to interpret the oxidation chemistry of DPE. In DPE oxidation, a high reactivity at low temperatures and two negative temperature coefficient (NTC) zones were observed. These behaviors are explained in this work by taking advantage of the obtained species information and the modeling analyses: the two NTC zones are caused by the competition of chain branching and termination reactions of the fuel itself and specific oxidation intermediates, respectively. Furthermore, the general requirements to have double-NTC behavior are discussed. A variety of crucial fuel-specific C 6 species, such as ketohydroperoxides and diones, were detected in the species pool of DPE oxidation. Their formation pathways are illuminated based on rate-of-production (ROP) analyses. Propanal was identified as the most abundant small molecule intermediate, and its related reactions have an important impact on the oxidation process of DPE. Both acetic acid and propionic acid were detected in high concentrations. A new formation pathway of propionic acid is proposed and incorporated into the kinetic model to achieve a more accurate prediction for propionic acid mole fractions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Observation of the decays 𝐵 + → Σ 𝑐 ⁢(2455) ++ $\bar{Ξ}^-_c$ and 𝐵 0 → Σ 𝑐 ⁢(2455) 0⁢ $\bar{Ξ}^0_𝑐$

We report the first observation of the two-body baryonic decays 𝐵 + → Σ 𝑐 ⁢(2455) ++ $\bar{Ξ}^-_c$ and 𝐵 0 → Σ 𝑐 ⁢(2455) 0⁢ $\bar{Ξ}^0_𝑐$ with significances of 7.3⁢𝜎 and 6.2⁢𝜎, respectively, including statistical and systematic uncertainties. The branching fractions are measured to be ℬ⁡(𝐵 + → Σ 𝑐 ⁢(2455) ++ $\bar{Ξ}^-_c$) = (5.74 ± 1.11 ± 0.4⁢2$^{+2.47}_{−1.53}$) ×10 −4 and ℬ⁡(𝐵 0 → Σ 𝑐 ⁢(2455) 0⁢ $\bar{Ξ}^0_𝑐$) = (4.83 ± 1.12 ± 0.3⁢7$^{+0.72}_{−0.60}$) ×10 −4 . The first and second uncertainties are statistical and systematic, respectively, while the third ones arise from the absolute branching fractions of $\bar{Ξ}^-_c$ or $\bar{Ξ}^0_𝑐$ decays. The data samples used for this analysis have integrated luminosities of 711 fb −1 and 365 fb −1 , and were collected at the ϒ⁡(4⁢𝑆) resonance by the Belle and Belle II detectors operating at the KEKB and SuperKEKB asymmetric-energy 𝑒 + ⁢𝑒 − colliders, respectively.

branching fraction↗
DOE OSTI2024

Measurement of the e + e − → π + π − π 0 cross section in the energy range 0.62–3.50 GeV at Belle II

We report a measurement of the e + e − → π + π − π 0 cross section in the energy range from 0.62 to 3.50 GeV using an initial-state radiation technique. We use an e + e − data sample corresponding to 191 fb − 1 of integrated luminosity, collected at a center-of-mass energy at or near the ϒ ( 4 S ) resonance with the Belle II detector at the SuperKEKB collider. Signal yields are extracted by fitting the two-photon mass distribution in e + e − → π + π − π 0 γ events, which involve a π 0 → γ γ decay and an energetic photon radiated from the initial state. Signal efficiency corrections with an accuracy of 1.6% are obtained from several control data samples. The uncertainty on the cross section at the ω and ϕ resonances is dominated by the systematic uncertainty of 2.2%. The resulting cross sections in the 0.62–1.80 GeV energy range yield a μ 3 π = [ 48.91 ± 0.23 ( stat ) ± 1.07 ( syst ) ] × 10 − 10 for the leading-order hadronic vacuum polarization contribution to the muon anomalous magnetic moment. This result differs by 2.5 standard deviations from the most precise current determination. Published by the American Physical Society 2024

Adachi, I. (ORCID:0000000322870173)↗
DOE OSTI2023

Impact of temperature on light yield and pulse shape discrimination of polysiloxane-based organic scintillators formulated with commercial resins

This work investigates how increased temperature affects neutron/ discrimination and light yield (LY) in several different polysiloxane-based scintillators doped with either 9,9-dimethyl-2-phenylflourene (PhF) or 2,5-diphenyloxazole (PPO) as a primary fluorophore and 9,9-dimethyl-2,7-di((E)-styryl) fluorene (SFS) as the secondary fluorophore. The polysiloxane matrices were prepared from the commercial resins Wacker Lumisil 579 or Shin-Etsu KER-6000. Control scintillators were prepared from poly(vinyltoluene) (PVT), the industry standard matrix, as a reference point for LY and pulse shape discrimination (PSD) measurements. Samples with PhF and PPO dopant concentrations of 1 wt% and 5 wt% in the polysiloxanes and 3 wt% and 5 wt% in the PVT samples were tested at 20 °C, 35 °C, and 50 °C. In the polysiloxane samples, the KER-6000 resin outperformed the Wacker 579 and PhF proved to be a better dopant than PPO in both LY and PSD capabilities. Polysiloxane scintillators showed slight decreases in LY and increases in neutron/discrimination at increased temperatures, while PVT scintillators showed a similar LY decrease with little to no improvement in neutron/discrimination at increased temperatures. Altogether, polysiloxane scintillators may not require recalibration in applications where temperatures increase up to 50 °C.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗